This invention is directed to marking apparatus, and in particular, to apparatus for imprinting intermittently advanced webs. Many packaging techniques utilize intermittently advanced webs of material. These webs may be formed of plastic, paper, foil and the like. Frequently, two sheets of such web material are intermittently fed to the packaging machine, the material to be packaged is fed between the sheets, and the periphery of the sheets or compartments within the sheet are sealed to define a plurality of separate packages. It is frequently necessary to insure that certain imprinting appears in proper registration on each of the packages thus formed, such as trademarks, instructions for use, and lot and dating information. Imprinting after the formation of the package is generally not practical, and accordingly, it is necessary to imprint on one or both of the webs defining the package at particular predetermined locations on the web, which locations are selected in coordination with the operation of the packaging machinery.
In the art, several methods have been attempted in order to perform such imprinting in coordination with the packaging machinery. Such attempts have included printing using rollers operating during displacement of the webs and flat plate printing operating while the web is stopped. Neither of these approaches have proved fully satisfactory in all applications.